Serializer/Deserializer (SerDes) circuits facilitate transmitting parallel data over a serial link between two points by converting parallel data into serial data for transmission and converting the received serial data to parallel data. This allows fewer physical interconnections to be necessary between the two points.
An electronic system is considered to be mesochronous if the two points share a common clock signal and thus share the same clock frequency. An electronic system is considered to be plesiochronous if the two communicating points use different sources for the synchronizing clock. A SerDes transceiver or link is typically a plesiochronous system. Because the two points do not share a common clock, a complication of using SerDes circuits is synchronizing data transmitted via a clock at the transmitting end with a clock generated by a different source at the receiving end. The frequencies of the two clocks may be slightly different and may vary over time. This is often referred to as frequency drift or frequency wander. Frequency drift makes it difficult to align received data with a local clock because the frequency of the clock at the transmitting side may drift with respect to the clock at the receiving side.